1. Field of the Invention
The present invention relates, in general, to magnetic tape head assemblies for use in conjunction with magnetic contact recording media, and more particularly to a tape head with a transducer support assembly with protective edges, i.e., at the leading and trailing edges, adjacent the core to create an increased height or radius adjacent the core and read/write gap to enhance air removal and to provide wear protection for the softer core materials during high speed operations with a number of recording media or tape having varying stiffness.
2. Relevant Background
Magnetic head assemblies typically contain one or more raised strips or supports that have surfaces over which the magnetic recording media, e.g., tape, passes. Embedded in each support surface is a transducer which may be a recording transducer (i.e. recording or writing head) for writing information (i.e., bits of data) onto the media or a reproducing transducer (i.e., reproducing or reading head) for reading information from the media. An embedded recording transducer produces a magnetic field in the vicinity of a small gap in the core of the recording transducer that causes information to be stored on the magnetic media as it streams across the support surface. In contrast, a reproducing transducer detects a magnetic field near the surface of the magnetic media in the vicinity of a small gap as the media streams over the support surface.
There is typically some microscopic separation between the gap of the transducer core and the recording media. During operation, this separation must be tightly monitored and controlled to avoid or minimize xe2x80x9cspacing loss.xe2x80x9d The separation reduces the magnetic field coupling between the recording transducer and the media during writing and between the media and the reproducing transducer during reading. The magnetic field coupling decreases exponentially both with respect to increases in the separation between the media and the support and with respect to increases in the recording density. The amount of media area required to store a bit of data is a factor in determining recording density and as less media area is required to store a bit of data, the recording density increases. Thus, while a higher, more easily obtainable amount of head-to-media separation may be acceptable at low recording densities, the growing demand for higher recording densities has led to the need for tighter control over the head-to-media separation that can be tolerated to obtain useful levels of magnetic coupling.
To control spacing loss, a tension is applied to the tape as the tape passes at a wrap angle around a support surface and an adjacent transducer core surface each having a height and a width. Due to this tension, the tape exerts a pressure against the support surface, and if the support surface and core surface have uniform widths and heights, the pressure is substantially uniform along a longitudinal axis of the support. The pressure is essentially proportional to the tension and the wrap angle and inversely proportional to the support width.
In some tape head assembly designs, the pressure is intentionally increased to control spacing loss. For example, the pressure can be increased by increasing the tension in the tape, by modifying the wrap angle of the tape on the support surface, and/or by modifying the width of the support surface. However, increased pressure is accompanied by negative consequences including reduced tape life, increased possibility of tape damage and data loss, and support and core surface wear leading to a shortened head life. Moreover, increased pressure can result in uneven wear along the support surface, which can be particularly troublesome between regions of the support and the transducer core. As can be appreciated, increased and uneven wear rates become more serious problems as operational speeds for magnetic head assemblies are increased.
Operational problems with head wear and uneven wear have recently grown with the use of magnetic media having varying stiffness. For example, a magnetic head assembly may be used to read and write to a magnetic tape with a given stiffness that causes the magnetic tape to have a corresponding natural radius and contours. The support surfaces and core typically will wear to fit better this radius and natural contours of the tape. When the magnetic head assembly is then used with a magnetic tape having a different stiffness, e.g., a higher stiffness tape, a larger and sometimes unacceptable separation distance may initially exist until again the magnetic media is worn or broken in to match the new tape stiffness. Hence, there is a need for a magnetic head assembly that address the need for wear control that is also useful for magnetic media of varying stiffness.
Several magnetic head assembly designs have been developed in attempt to address these wear problems. In many tape head assembly designs, the pressure at the core is increased to enhance magnetic coupling by providing an elongated support assembly in which the width of the core and adjacent surfaces is less than the width of the adjacent elongated support surfaces. This smaller width makes the pressure applied non-uniform along the longitudinal axis of the support with higher pressure being applied at the core area and providing a better contact area. Unfortunately, this head design often results in higher wear rates at the core area that may lead to uneven wear within the support assembly. In some cases, higher core wear rates and pressures have been addressed with the use of wear resistant materials for the core center and/or in the adjacent supporting surfaces that are either parallel to the travel path of the media over the core or on all sides of the core.
In a different design approach, the support area near the core is made wider than the adjacent elongated support surfaces to obtain a softer or lower pressure mating of core and magnetic media. Wider core area designs are described in detail in U.S. Pat. Nos. 5,426,551 and 5,475,533 to Saliba, which are both incorporated herein by reference. The wider support surface near the core results in less pressure being applied at the core which is beneficial in controlling uneven wear. The wear rate is further controlled by providing wear surfaces of glass or other nonmagnetic material adjacent the magnetic ferrite core positioned parallel to the travel path of magnetic media. The wear rate is self-regulated to be relatively uniform along the longitudinal axis of the support assembly because the pressure is less than on the elongated support surfaces that are fabricated of a more wear resistant material. While addressing some industry problems, these wider core area devices tend to function well initially but then also develop problems of uneven wear on support surfaces and of core wear as the entire support assembly experiences wear. Additionally, the height of the core and adjacent wear surfaces typically are selected for a particular media and media thickness and experience wear that makes the device better suited for continued use with that media rather than for several media with varying stiffnesses.
Additionally, air flowing under the magnetic media during higher speed operations can cause spacing losses, and airflow needs to be addressed during magnetic head assembly design. During operation, air is moved within the magnetic head assembly as the magnetic media rapidly advances across the surfaces of the assembly facing and supporting the magnetic media, such as the support surface and the core. Spacing losses can develop when the flowing air passes between the core and read/write gap and the magnetic media. In the narrower core area devices, air tends to be channeled over the core because it first strikes the wider adjoining support surfaces and then is forced into the narrower core area. The wider core area devices provide better airflow control with the air first striking the wider core area and being channeled away towards the adjacent, narrower support areas where reading and/or writing is not occurring. However, for both types of head assemblies, the use of numerous magnetic media with differing stiffness often results in airflow problems that result in spacing losses. Also, over the lifetime of the head assemblies, wear (and particularly, uneven wear) often results in changing airflow paths that can lead to airflow problems even in devices that initially functioned effectively.
Hence, there remains a need for a magnetic head assembly that better controls airflow over a magnetic core and provides enhanced wear control in surfaces contacting the magnetic media, which may have varying stiffness.
The present invention addresses the above discussed and additional problems by providing a wider core area design for a transducer support assembly that controls uneven wear problems while also providing improved airflow control to limit spacing losses (e.g., to minimize xe2x80x9cfloatingxe2x80x9d separation). The inventor recognizes that the use of a wider core area relative to narrower adjacent, elongated support surfaces often results in the contact pressure applied by the media, e.g., magnetic recording tape, being concentrated at the edges of the wider core area, i.e., core support. Hence, as the tape passes over the transducer support assembly, the edges (note, both edges act as leading and trailing edges depending on the direction of travel of the media) are worn down at a faster rate, which can cause airflow problems and spacing losses.
To address this problem that is generally unique to wider core area designs in tape head assemblies, the core support is initially manufactured to include wear surfaces of a harder, more wear-resistant material at the two leading/trailing edges to extend the useable life of tape head assemblies. In a preferred embodiment, the wear-resistant edge members are raised (or, alternatively, the edge members may initially be coplanar with softer adjacent wear surfaces and allowed to become raised due to wear occurring in an initial break-in wear period) to provide a larger height than the core. After a break in or initial wear period the edge members and core contact surfaces become generally arcuate in cross-section with the initially larger radius of the edge members controlling wear on core. In operation, the arcuate surfaces typically form a single continuous curved surface with a single radius that contacts the recording media. Having an edge member that always has a larger or equal radius to the adjacent core surface is especially beneficial for high speed operations as it better directs airflow (e.g., strips away air being moved with the tape from the core area) and protects the transducer core from wear.
More particularly, a magnetic head is provided for writing to and reading from magnetic recording media, such as tapes of varying stiffness. The head includes first and second elongated supports spaced apart on a facing surface and having support surfaces extending along a longitudinal axis. During operation, the magnetic recording media travels transversely across the support surfaces applying a contact pressure. A core support is positioned between the two elongated supports. The core support has a width as measured perpendicularly to the longitudinal axis of the support surfaces that is greater than the widths of the support surfaces thus creating a nonuniform pressure distribution along the longitudinal axis (e.g., when contact surfaces are coplanar or the same radius, greater pressure is applied on the narrower support surfaces).
The core support includes a transducer core with an elongated contact surface positioned to extend transverse to the longitudinal axis of the support surfaces. An edge member is positioned adjacent the contact surface of the transducer core to control wear and direct airflow. In this regard, the edge member includes a wear surface for contacting the media that is fabricated of a material, such as aluminum titanium carbide or zirconium, that is harder and has a greater wear resistance than the transducer core. In a preferred embodiment, a second edge member is provided on the opposite side of the contact surface of the transducer core to accommodate multiple tape travel directions. After initial fabrication, the wear surfaces of the edge members are substantially coplanar and raised relative to the contact surface of the transducer core and the support surfaces. Additionally, the contact surface itself may be raised relative to the support surfaces with these two surfaces have similar hardness and wear resistance characteristics (e.g., both surfaces may be magnetic ferrite or the like). In this manner, the magnetic head provides self-regulating wear regions that adjust to distribute the contact pressure and wear such that the wear surfaces of the edge members are generally raised relative to the contact surface of the transducer core and the support surfaces.
After break in and during the operational life of the head, the wear surfaces of the edge members are arcuate with a radius that is larger than the adjacent wear surfaces. In this fashion, the edge members control the contact with the magnetic media and the rate of wear in the adjacent protected core area. The contact surface of the core that was initially lower than the wear surfaces of the edge members eventually becomes arcuate and has a radius that is substantially equal to or slightly less than the wear surfaces of the edge members. The contact surface of the core and the wear surfaces of the edge members generally form a continuous contact surface that is raised (or at a larger radius) than the adjacent elongated supports to provide good coupling and contact with the recording media.